iOS (Jailbroken): FlashCam sticks two extra buttons on your iOS lock screen that give you quick access to your camera and an LED flashlight.

They say the best camera is the one you have with you, though it doesn't do you much good if you take 10 seconds to find it. You may not need your camera or flashlight that often, but when you do, you need them quickly. FlashCam puts a button for each right on your lock screen so you can access them right away.

To install FlashCam, just open up Cydia and go to Manage > Sources. Add the http://cydia.wrightscs.com repository, then search for FlashCam in the Cydia database. You'll find it in your Settings app, where you can tweak where it shows up on the screen, which camera app it uses, and more. Note that I found it to conflict with the Activator extension used by many other jailbreak apps, so if you use anything that relies on Activator, your mileage may vary.